Buildings such as the Shard, near London Bridge, do little but diminish joy.

"Urban planning”: two words designed to strike dread into the heart of any Tory. Urban planning is John Prescott made concrete: the reduction to rubble of Victorian streets and their attendant green spaces, and their replacement with high-rise blocks artfully arranged to resemble butterflies – for any resident able to hire a helicopter, in order to view their home from above. That most residents lack such a bird’s-eye view is something Frederick Gibberd, who designed such a butterfly block in Harlow, must have overlooked; as did whoever’s responsible for the monstrous Shard at London Bridge, foul stab into the heart of London that it is.

Despite the Conservative antipathy to planning, the Prime Minister recently announced his desire to build more garden cities – more new towns – to house our burgeoning population. Leave aside the, ah, external factors that drive the population increase. Are planned towns inherently un-Tory? Not if two new “new town” principles are adopted.

The first, counter-intuitively, is to minimise the need for new urban conurbations at all, by halting the decline of the existing city centres. In that respect, Michael Gove will likely achieve more substantive urban regeneration (another dread phrase) than any other living politician. It is the lack of good schools that drives the middle classes from the inner city, and the consequent downward spiral of the economic and social infrastructure is the start of the vicious circle that makes so many of us head for the suburbs. Mr Gove’s free schools and academies will do more to slow down the exodus of the economically active from the city than any other policy. Every working couple with children that remains in the existing city is one fewer family required to be housed in a new town.

All that – the liberation of schools from state control, leading to better places to live, as well as better Sats scores – might suggest the second principle: not to let the planners get carried away. It must be tempting to look down at a map of a proposed town, and carve up the space rationally: “The houses go there, the light industry there, the cinema multiplex and Carphone Warehouses here.”

I suspect it’s that over-zoned aspect which made the existing new towns less than perfect, at their start. One of the frustrations I had living in Harlow was that the train station was so far from my house that I had to drive to it, which sort of defeated the purpose. And to get from any one “zone” to another by public transport usually required taking a bus into the centre, and back out again, a “hub and spoke” model that revealed the extent to which the town was planned before any messy humans were sent to live in it.

That lack of a human perspective is clear also in Stevenage, the new town where I work. I drive up from north London in the morning and use the town’s excellent swimming pool (good planning). But if I want to visit a coffee shop afterwards, even one just a few hundred yards away, it’s quicker to drive, rather than walk; there’s no direct pedestrian route, just dual carriageways, chopped up with those ubiquitous new town roundabouts, and unappealing subways. It probably looked really cool on an architect’s plan, though.

Roger Scruton wrote an important article recently about the missing dimension in modern urban planning models. What I think of as the “human perspective” (town centres you can walk around, and, moreover, want to walk around), he identifies, correctly, as beauty: “To plan or not to plan is a false choice. Instead, civic leaders should think in terms of fostering beauty through the use of aesthetic constraints.”

By this he means not that we should just sit back and let urban space go with the human flow; that way lies the autogeddon of Cities For Cars: Stevenage on a US scale. Planning, pace our Tory instinct, matters. He means, I think, establishing an aesthetic version of the broken-window principle that has proved so successful in setting criminal justice priorities. Just as letting a broken window pass unchecked invites vandals to claim a space as their own, so the insertion of a concrete high-rise where once stood a row of Victorian terraces – or a hideous jag of sky-scraping glass, slap on the bank of the Thames – does the same to the human spirit: it diminishes joy.

As Professor Scruton puts it, our town centres degenerate when they are “built so that appearances do not matter, when utility stares from every glass façade, and when the demands of the human eye are everywhere repulsed or ignored”.

In fact, the first new towns achieved a particular aching beauty, because the people who live in them refused to be cowed by concrete and glass; places like Harlow have transcended their over-planned origins. Better for the next generation of new towns if they don’t repeat the concrete mistakes of their predecessors.